This invention generally relates to the field of disk drives, and more particularly to forming optimal structures for bonding in a head gimbal assembly using anisotropic conductive adhesive.
With the rapid progress of miniaturizing and thinning technology for electronic devices, high-density inner wiring systems including flex-print circuit (FPC) have become essential. At the same time, micro-connecting technology for the connection of FPC with other electronic parts, such as the traces on a magnetic head suspension assembly, is indispensable.
Traditionally the FPC is capable of adopting ultrasonic bonding. The connecting terminals of the FPC are plated with gold; the flying leads of the FPC are aligned with and pressed to the bonding pad on the suspension with sufficient force to keep the alignment and atomic interdiffusion of the flying leads and the underlying metallization, which process ensures the intimate contact between the two metal surfaces. However, the pressing of the flying leads of the FPC entails complex processing, and ultrasonic bonding to different bonding pads is very difficult to contact Moreover, bonded parts cannot be separated in the future to be reworked without damaging the FPC or the suspension.
Alternatively, FPC can be solder-bound using solder bumps produced by, for example, plating processes, for interconnections. However, this process requires forming metal cores and solder bumps for soldering. The metal cores incur extra expenses, and soldering has to be performed at high temperatures typically over 180 degrees Celsius.
Furthermore, both ultrasonic bonding and soldering are becoming increasingly expensive because of high cost of labor and parts of the FPC. There is therefore a need for a bonding method which achieves a stable, reworkable connection without complicated processing.